In the past 100 years or so, electrical or electronic circuits, have seen a dramatic change in their design and their assembly process. About 100 years ago, DC powered circuits were hard wired and hand soldered in a box format. The high current electronic or electrical components were fastened to the box and then they were manually connected by hand soldering wire of sufficient diameter to carry the required currents and voltages. In many of these circuits the large sized, multi voltage batteries were placed in a battery compartment and then they were also hand soldered into the circuit. Typical battery sizes could be a 6 volt lantern battery or a battery pack made of multiple 6″ size unit cells or even possibly some smaller sizes. When the batteries were depleted, they were desoldered and replaced in the same manner as when the circuit was made.
About 60 years ago with the invention of the transistor and other electronic parts, the design and manufacturing of circuits changed drastically. Due to the electronic changes, which required much lower currents and many times lower voltages, circuits could be made in a more efficient and compact manner. This allowed circuits to be made on a circuit board in a wave soldering method. As part of this wave soldering assembly method, battery holders were also included into the circuit. Due to the big reduction in required voltages and currents the power source size could also be reduced in size. Typical power sizes could now be D, C, AA, AAA, transistor 9 volt battery or even coin or button cells. In these new circuits with the battery holder, the consumer could install the battery when he begins using the device as well making it very easy to replace the depleted batteries.
In recent years, as described in several Blue Spark patent applications, printed electronics on flexible substrates has become a new process and is growing in popularity. In this process, some or all of the circuit is printed as well as some of the electronic components. Typically this type of circuit could include a display, IC chip, sensor, antennae, lights and a relatively low capacity power source such as a flat printed battery. In some applications, the power source could also be printed in a totally integrated manner.
Alternatively, the power source can be integrated in a different manner. In order to reduce costs, the power source can be a printed or otherwise constructed as a flat battery that is provided as a complete cell or battery for later integration into the desired circuit. A typical cell can provide, for example, about 1.5 volts DC. Where greater voltages are required, it is conventionally known to connect two or more cells in series to increase the voltage. Similarly, multiple cells can be connected together in parallel to increase the effective capacity. For example, a battery can include two cells electrically connected in series to provide 3 volts DC. Still, it is desirable to reduce the overall size of the battery, even with multiple cells, for use in small circuits. Various designs and methods of manufacture of a flat cell and batteries are described in co-pending U.S. application Ser. No. 11/110,202 filed on Apr. 20, 2005, Ser. No. 11/379,816 filed on Apr. 24, 2006, Ser. No. 12/809,844 filed on Jun. 21, 2010, Ser. No. 13/075,620 filed on Mar. 30, 2011, Ser. No. 13/625,366 filed on Sep. 24, 2012, and Ser. No. 13/899,291 filed on May 21, 2013, as well as issued U.S. Pat. Nos. 8,029,927, 8,268,475, 8,441,411, 8,574,745 all of which are incorporated herein by reference.
With the growing market needs for low cost, low capacity thin flat cells, it would be beneficial to produce a thin, flat, printable flexible cell that is versatile and inexpensive to mass-produce. Printable, disposable thin cells that are well suited for low-power and high-production volume applications would be useful, especially if they offer adequate voltage, sufficient capacity, rate capability, and low-cost solutions. Conventional low-profile batteries typically have few of these attributes, if any.
Furthermore, in recent years there has been a growing need for various electronic devices, such as active RFID tags, sensors with RFID tags, skin patches with sensors to detect body temperature, as well as electronics to log and wirelessly transmit and/or receive such data, skin patches that deliver iontophoretic or other electrical functionality, etc. These various electronic devices can have various electrical loading characteristics. Thus, it can be beneficial to provide thin flat power sources that can reliably deliver relatively higher currents. In one example, the thin flat power sources can be separately manufactured and later electrically coupled to various electronic devices. In another example, the manufacture of the thin flat power sources can be integrated with the manufacture of the desired circuitry of electrical components to power the components.